1. Field of the Invention
The present invention relates to a processing method for a high pressure gas container. More specifically, it relates to a processing method for a high pressure gas container with a certain amount or less of the Si amount in the inner surface uppermost layer part, and a halogen containing gas filled in the high pressure gas container. Further specifically, it relates to a processing method for a high pressure gas container of applying a pressure test by hydraulic pressure, and polishing the inner surface thereof to a certain depth, and a halogen containing gas filled in the high pressure gas container.
2. Description of the Related Art
The halogen containing gases are used as a doping agent for the semiconductors, a dry etching agent, or a cleaning gas for a CVD device, and high pureness is required for the halogen containing gases used for these applications. To a filling container for these highly pure gases, the inner surface polishing process is applied frequently for preventing adsorption of water or impurity gases to its inner surface and keeping the high pureness of the filled gas. However, among the halogen containing gases filled in the container with the inner surface polishing process applied, there are sometimes those having the impurity concentration raised according to passage of time. One of the impurities is water, and the other one is a halogen containing unknown impurity.
As a result of our research for the cause of the increase of the water content in the gas according to the passage of the time, it was learned that the trouble of the water content increase by the time passage can easily be generated in the case the container after having the pressure test by the hydraulic pressure is used. As a result of the further detailed analysis, it was revealed that a water content, which cannot be removed by the drying process, remains in the container after the pressure test by hydraulic pressure, and the water content is introduced gradually into the gas filled in the container so as to increase the water content in the target gas according to time passage. Although there is a method of vacuuming the inside while heating the container, or the like, the water content cannot be removed completely, and an effective means of removing water has been desired.
Moreover, as a result of our research of the cause of the increase of the halogen containing unknown impurity by the time passage, it was learned that generation of the phenomenon is concentrated in the container after applying the internal surface polishing. There are various methods for the internal polishing, and a method of using a polishing agent is often adopted for its inexpensiveness and easiness. After executing the internal surface process using the polishing agent, in general, it is washed with water and/or a solvent, dried, and has a valve mounted so as to be used as a gas container. According to the halogen containing gas filled in the container with the internal surface treatment with the polishing agent, a problem is involved in that the purity is lowered by the increase of the unknown halogen containing impurity according to the passage of time after filling.